Process for the transformation of gypsum



V Patented Jan. 27, 1 931 UNITED STATES rnrrz Borne, or AACHEN, AND HANS BRENnk, or P032, NEAR coLoGniiemmA i l,

ASSIGNORS 'ro BHENANIA VEREIN onmvr sonnn rnnnrxmv A. GWQF conceive, GER-l MANY No Drawing. Application filed November 3, 1925, Serial life} {66,640, and. inGermany beceinber Sh i924.

Y The present invention relates to a process for the transformation or decompositionof gypsum and has for its object to secure as products of this decomposition sulphuric 50 pulverulent fuel. Instead of taking the rnocnss r03. THE TRANSFORMATION or eYPsUm steam'from'a special source itisi alsopossible to employ afuel rich in hydrogen being able to form, by its' combustion, the steam requlredfor the reaction, for instance oil, pro'- '5 acid and a Portland cement which contains ducer gas from ligniteetc. 55

practically neither undecomposed calcium I T v v sulphate nor excess clay. I v t It is known that it is possible todecom- {1100 a t'gof a'Wurttemberg hav- 7 pose gypsum undersimultaneous separation ing the following composition :1

10 of S by heating it with pure silica or sand.

it has also been proposed to decompose gyp- --5--5,-- V

sum by conducting steam over the material --{4 -4 heated to incandescence. We have found 2 that, by combining these two known meth- A12Q3 ---9--- 2 15 ods, the decomposition occurs more quickly a- -r (192% u and more completely if the mixture of gyp- 7 sum and silica or materials containing large ,Were mlxed h' Parts o a l y orlglnat" quantities of silica is heated at high temperalng f rom the Rhlneland and havmg thls ture preferably above 1100 C. in a current Posltlon: V v o 7 of inert gas, or preferably in an oxidizing at- 0&0 0.91% f;7-.0 mosphere to avoid any reducing effects and Sio I 65 237 in the presence of steam. By this process ""f""*** A1 0 22.97% V the sulphuric acid is spllt up as S0 and may O l a 1 117 be transformed in a known manner, the lime i ffi g being bound to the silica in the form of pri- H O :75

2 t 0 mary or-secondary calcium silicate according to the quantity of silica employed. The mixture was heated in a rotary-tube It is of particular advantage to use clay kiln ata temperatureof about 1200 degrees as the mixture comprismg silica inasmuch O, Th raw i t h d I th f ll i as it has been discovered that practically a l i 7 complete decomposition of the calcium sul- V Y fate is obtainable if clay is employed in such 0&0 -i---'---- quantities that CaO and SiO +Al O are at 3"- the ratio of, say, 2:1 which is preferably 2 used in the manufacture of cement. What 2 3 -;$,5 is incidentally obtained is a silicate free 'E z s-e p from the reduction products of the sulfate. S 2 1 Now if the clay or other raw materials con- Alkallne --V 40 tam iron in he 2 of an impurity; The fuel consisted of a producer gas obgg' gl g fg 6 g fiffg g g g gf gg tained from Rhenish lignite with a high per- 2 2 a l calculated for the existent quantit of iron 33t OfhYdFOgm and havmg lthls compo i as will correspond to the ratio 1Fe2d,:2ca0. S1 Ion 'We have also found that said decomposi CO 31 4% tion takes place most quickly and most com- CO 43% 5 pletely if the steam acts on the mixture in the CH4 1 moment of sintering. This manner of H 11 9 2 workmg can be effected by blowing the steam directly into the flame generated by gas or and during combustion so much a1r was admitted to the fuel that the waste gases were 2 q a i i 1,790,023-

free from carbon monoxide and of the following composition:

O02 18.0 SO2 3.94% 5 CO 0.00% 0 0.90%

The ensuing calcined product was practically free from sulfuric acid and contained only 0.6% of S0 Having now particularly described "and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is: v

5 1; The'process' for the decomposition of gypsum, which comprises mixing the gypsum with silica and heating the mixture in an oxidizing atmosphere to a temperature of more than 1100 C. by the aid of heating gases containingat least 15 Vol. of steam.

2. The process forthe decomposition of gypsum, which comprises mixing the gypsum with silica and heating the mixture in an oxidizing atmosphere to a temperature of more than 1100 C. by the aid of heating I gases containing at least 15 vol. of steam, which are formed by the combustion of fuel rich in hydrogen. 7

. .DR. FRITZ ROTHE.

- DR. HANS BRENEK. 

